Pitch blocks



E. L. LORENZ 2,916,074

FITCH BLocxs Dec. 8, 1959 med 061.15, 1956 2 sheets-sheet 1 INVENTOR @26a MM ATTORNEYS E. L. LORENZ 2,916,074

Dec. 8, 1959 FITCH BLOCKS Filed Oct. 15. 1956 2 Sheets-Sheet 2 lNv'EN'roR ATTORN EY lUnited States Patent O rrrcn BLocKs Eldon L Lorenz, Grand Rapids, Mich., assignor to Michigan Wheel Company, Grand Rapids, Mich., a corporation of Michigan Application October 15, A1956, Serial No. 615,83'1

Claims. (Cl. 153-32) This invention relates to a pitch block assembly for shaping helical bodies and more particularly screw type propellers.

Pitch blocks such as that shown by the United States `patent to Warren 2,013,705 are old. These pitch blocks -usually consist of a table supporting a post and a block. The propeller is supported by the post and its blade extends over the block having a contour of proper pitch .for the propeller. The blade is formed by working it on the block until it conforms to the shape of the contoured surface. These conventional type pitch blocks have worked satisfactorily when the center line of the blade passes through the axis of the hub. In such cases the position of the pitch block required no changing except in a radial direction from the support posts which is rela- `tively simple.

Diculties have been encountered in forming blades with center lines offset from the central axis of the hub. This requires movement of the pitch block or hub in a lateral or tangential direction. Since such accurate adjustment Was difficult, the operator frequently held the `propeller in his hand and gauged its position on the block by eye. Then as he formed the blade he periodically checked its shape and pitch on a gauge. This was a very tedious and time consuming operation and required a skilled and experienced operator.

The object of this invention is to eliminate these difculties and provide a pitch block assembly with which any mechanic can accurately form the blade to the proper pitch regardless of the center line offset of the blade.

Another object of this invention is to provide a simply constructed pitch block assembly having means for accurately positioning the forming block for various blade sizes, pitches and shapes.

Another object. of this invention is to provide a pitch block assembly having means for adjusting the center line of the block relative to the propeller support post whereby propeller blades having center lines odset from the axis of the hub can be properly and accurately shaped.

Another object of this invention is to provide a pitch block assembly having a novel gauge means for accurately positioning the blocks in relation to the propeller support posts.

Other objects of this invention will become obvious to one skilled in the propeller art by reading the following specification in conjunction with the accompanying drawings wherein:

Fig. l is a plan view of the pitch block assembly.

Fig. 2 is a side, elevational view of the pitch block assembly.

Fig. 3 is a fragmentary, cross sectional, elevational view taken along the plane III-III of Fig. l.

Fig. 4 is a fragmentary, cross sectional, elevational vview taken along the plane IV-IV of Fig. 6 and illustrating the pitch block in a different position than that of Fig. l.

invention. Y

Fig. 6 is a partially cut away plan view of the pitch block assembly in a dilerent position than that of Fig. l.

Fig. 7 is a plan view of a base plate which isa part of the assembly.

Fig. 8 is a cross sectional, elevational view taken along the plane VIII-VIII of Fig. 7.

Fig. 9 is a cross sectional view taken through a pitch block having a high pitch.

Fig. 10 is another sectional view taken through a different pitch block having a low pitch.

Briefly, this invention relates to a pitch block assembly having a base and a pitch block mounted on the base. A tongue and groove connection exists between the base and the pitch block.' The tongue is narrower in width than the groove, thereby providing spaces between the walls of the groove and the tongue. Gauge means having two ngers adapted to t one and each of the spaces is provided. The width of these fingers determines the position of the pitch block on the base.

The base is mounted on a table which is also supported by a post adapted to receive a propeller. The relative positions of the post and base are such that the axis of the post and the centerline of the base is constant. Thus, varying the position of the pitch block on the base varies its position relative to the post. The gauge means determines such position and thus properly positions the pitch block for diierent sizes and shapes of propeller blades.

Referring to the drawings, the numeral 1 denotes the composite pitch block assembly which includes the table 10, the base plate 20, the mounting plate 30 and the pitch block 40. The table, also supports the post 50 adapted to receive a propeller.

The table 10 is a thin slab or a at piece of solid material, preferably metal such as steel, having a smooth top surface and a groove 11 extending lengthwise thereof. The groove 11 receives a tongue 21 extending downwardly from the lower surface of the base plate 20.

The base plate 20 is a relatively thin slab of solid material having a smooth undersurface except for the tongue 21 which is located on the center line of the base plate 20. The top surface of base plate 20 has a groove 22 defined by the side walls 23 and the bed 24. The surface of the bed 24 has a plurality of shallow grooves provided for the purpose of decreasing the surface area which the tongue 31 of the mounting plate 30 contacts. The base 20 is pie-shaped. However, any other suitable shape is satisfactory.

Two holes 25 are provided in the groove 22 for receiving screws 26 that attach the base plate 20 to the table 10. Base plate 20 also has a hole 27 on each side of the groove 22 for receiving the bolts 28 that secure the mounting plate 30 to the base plate.

The mounting plate 30, to which the pitch block 40 is secured, is substantially the same size and shape as the hase plate 20. It has a flat bottom surface with an elongated tongue 31 extending downwardly into the groove 22 of the base plate. The tongue 31 and groove 22 provide a tongue and groove connection between the two plates.

The relative widths of the tongue 31 and groove 22 are important. The tongue 31 is substantially narrower than the groove 22, although the depth of the two is substantially identical. The relative sizes of the tongue 31 and groove 22 provide spaces 32 and 33 between the walls 23 of the groove 22 and the tongue 31.

The spaces 32 and 33 are adapted to receive the gauge 60 (Fig. 5) which includes two lingers 61 and 62 connected together at one end by the cross piece 63. The spaces 32 and 33 are adapted to each receive one of these fingers. As illustrated in Fig. 3, space 32 receives nger 61. Space 33 receives finger 62.

The mounting plate has a groove 34 on its top surface. A plurality of tapped holes 3S are spaced along the groove 34 for receiving bolts that secure the pitch block to themounting plate. On each side of groove 34 is a slot 236 running perpendicular to groove 34. This slot receives the bolts 28.

The pitch block 40 is a cylindrical member having a flat bottom except for the tongue 41. The bottom surface rests on the mounting plate 30 with tongue31 seated in the groove 34 on the top surface of the mounting plate. The pitch block 40 has two holes 42 for receiving -bolts 43 that engage the threaded holes of the mounting plate. The tongue 41 is adjustable in the groove 34 of the vmounting plate and adapted to be locked in one of several different positions determined -by the position of .the holes of the mounting plate. The contoured top surface 44 of pitch block 40 is of the proper size and shape for receiving the propeller blade above it. It is sized and pitched to correspond with the desired size, shape and pitchy of the blade. Therefore, a plane A .through the center line of block 40 includes the centerline C of the propeller blade. The center line of the blade is frequently offset from the axis of the propeller hub. Accordingly, the plane A through the center of the pitch block is frequently required tot be offset the same amount from the center axis X of the post 56.

Fig. 1 illustrates a pitch block and propeller P having their center lines C passing through the axis of the hub H and the axis X of post 50. Correspondingly, plane A passes through the axis X of the post 50 (Fig. 3).

Fig. 6 illustrates an example wherein the center line C of the blades is offset from the center axis of the hub. As a result, for proper shaping of the blade, the plane A of the pitch block is required to be offset from the axis X of the post 50 (Fig. 4). This invention provides a means for accurately positioning the pitch block to correspond with the center line offset of the blade.

The positioning of the pitch block 40 is determined by the size of the gauge 60 and more particularly by the width of the fingers 61 and 62. The total width of the two fingers is always equal to the total width of the spaces 32 and 33. yWhen the center line of the blade intersects the axis of the hub, the center line A of the pitch block intersects the axis X of the post 50 (Fig. l). Then the widths of the two fingers 61 and 62 are equal.

On the other hand, when the center line of the blade is offset from the axis of `the hub, the center line and plane A of the pitch block is offset from the axis of the .post 50. Then one of the fingers of the gauge 60 is wider than the other finger.

Figs. 4 and 6 illustrate this arrangement wherein linger 61a is wider than the finger 62a. Thus, the plane A of the pitch block is .offset from the axis X of the post 50. A plurality of different size gauges are provided for use in the pitch'block assembly. Each of these gauges is for different propellers having different center line offsets.

Operation Having described my invention, the operation is evident and simple. The base plate 20 is securely attached to the table 10 by screws 26. Thus, its position relative to the post 50 always remains constant. As a result, varying the position of the mounting plate relative to the lhase pl-ate 20 changes the relative position of the pitch block 40 .and post 50.

The operator .loosens the screws 28, permitting the mounting plate 30 to be moved laterally of the base plate 20, that is, with the gauge 60 removed. Then the proper size gauge is selected to correspond with the offset of the blade to be repaired or shaped. The mounting plate 30 is then slid onto the base plate 20 to a position where the fingers 61 and 62 of the proper size gauge can be insertedin the spaces-32 and 33 formed between the walls of the groove 2.2.and .the tongue 31. Having inserted the gauge 60, the screws 28 are then tightened and the pitch block is in the proper position to correspond with the desired offset of the blade center line.

The pitch block 40 is then adjusted in a longitudinal direction in slot 34. In such adjustment the tongue 41 rides in the slot 34 until the proper longitudinal position of the pitch block is reached. At this position, the holes 42 in the pitch block are aligned with the holes 3S in the mounting plate 30. The screws or bolts 43 are then tightened for securing the pitch block 40 in this position. The pitch block assembly is then ready for use in shaping the propeller blades. The hubI of the propeller P is inserted on the post 50 and rotated to cause one blade of the propeller to be over the pitch block. Then the operator works the blade by pounding it on the pitch block until the desired shape and pitch is obtained. This is repeated for all the blades.

This apparaus completely eliminates the requirement of the operator to periodically check the shape of the blade. Once the assembly is properly set, each blade can be fully shaped to its proper size and pitch.

This apparatus is particularly adapted for use on the field for repairing worn, fractured and misshaped propellers. It does not require a skilled operator to shape the blade. Any ordinary mechanic can operate and shape the blade by selecting the proper size gauge and properly setting the assembly. The gauges are all numbered to correspond with certain propellers so that selecting the proper gauge is simple.

Having described my invention, it should become obvious that, although Ihave described one preferred embodiment, other embodiments and modifications are possible within the broadest aspect of this invention. Therefore, all modifications coming within the spirit of this invention are covered by this patent unless the appended claims, by their language, expressly state otherwise.

I claim:

l. A pitch block assembly comprising: a base, a pitch block mounted on said base; holding means adjacent said pitch block for holding a workpiece; a tongue and groove connection between said base and pitch block; said tongue being narrower in width than said groove thereby providing spaces between the walls of said groove and said tongue; gauge means having two fingers adapted to fit one in each space; the width of said fingers determining the position of said pitch block on said base relative to said holding means.

2. A pitch block assembly comprising: a base; a pitch block mounted on said base; a tongue and groove connection between said base and pitch block; said tongue and groove each being elongated and running along a longitudinal line of its respective base and pitch block; said tongue being narrower in width than said groove thereby providing spaces between the walls of said groove and said tongue; gauge means having two elongated parallel fingers adapted to be inserted one into each space; the width of said fingers determining the relative positions of said longitudinal lines; and a post for receiving and holding a propeller; said post being located adjacent said base, the axis of said post intersecting the longitudinal line of said base.

3. A pitch block assembly comprising: a base; a pitch block; a mounting plate for supporting and mounting said pitch block on said base; holding means adjacent said mounting plate for holding a work piece; means for adjusting the longitudinal position of said mounting plate on said base; a tongue and groove connection between said base and mounting plate; said tongue being narrower in width than said groove thereby providing spaces between the walls of said groove and said tongue; gauge means having two fingers adapted to fit one in each space; the width'of said fingers determining the position of said mounting plate and said pitch block on said base relative to said holding means.

4. A pitch block assembly comprising: va base; a post for holding a workpiece; a table for supporting said base and post so that the relative positions of the axis of said post and the center line of said base is constant; a pitch block; a tongue and groove connection lbetween said pitch block and said base; said tongue being narrower in width than said `groove thereby providing spaces between the walls of said groove and said tongue; gauge means having two fingers adapted to it one in each space; the width of said fingers determining the relative positions of the center lines of said base and said pitch block thereby determining the relative position of the pitch block center line with the axis of said post.

5. A pitch block assembly comprising: a base; a post for holding a workpiece; a table for supporting said base and post so that the relative positions of the axis of said post and the center line of said base is constant; a pitch block; a tongue and groove connection between said pitch block and said base; said tongue and groove each being elongated and running along the longitudinal center line of its respective base and pitch block, said tongue being narrower than said groove, thereby providing space between the Walls of said groove and said tongue; gage means having two fingers adapted to fit one in each space; the Width of said fingers determining the relative positions of the center lines of said base and said pitch block thereby determining the relative position of the pitch block center line with the axis of said post.

Warren Sept. 10, 1935 Edwards et al. Jan. 22, 1946 

